Usually manips start with a lift. Try to make it so when you are hitting him in the air, make sure you keep your flow, and give uke a flow as well. Manips are usually preferred without grabbing, so don't grab. If you have a fair distance between you and uke, you can try to launch off to him and then tear him to shreds. Boomshots is a whole different topic, but to get a boom you need power and aim, and I won't really go into detail in this, but you could find someone to give boom tips.